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'Solar powered' nanofibre factory pulls CO2 out of the air

A new technique for pulling carbon out of the atmosphere and turning it into valuable nanofibres is being mooted as a potential 'cure' for CO2 emissions -- though scientists remain sceptical it could make a practical difference to the climate.

The new method, called the Solar Thermal Electrochemical Process or STEM, uses a solar-powered system that runs volts of electricity through molten lithium carbonate, which has lithium oxide dissolved in it. As electricity is applied the reaction produces oxygen gas, carbon nanofibres made of carbon atoms -- which form around one of the electrodes -- and lithium oxide, which can be used again in the reaction.

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Carbon nanofibres are extremely light and strong, and have applications in everything from batteries and electronics to manufacturing, aerospace and building materials.

Previous systems had struggled to make the process cheap and efficient enough for large scale production, but professor Stuart Licht of George Washington University claims his team's new method could be scaled up if given enough backing.

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Licht told the American Chemical Society in Boston that his prototype can make 10 grams of carbon nanofibres per hour, all using solar power. By varying the amount of current and the composition of the ingredients, the team was able to adjust the types of fibres used. Currently similar fibres sell for about $25,000 (£16,000) per ton, but Licht reckons his technique could bring that down to just $1,000 (£640).

[This is\c a reasonable path to bring down CO2 levels in the atmosphere.Stuart Licht, GWU

Published in Nano Letters, the group's idea has one big drawback; currently the nanofibres are not usable, because they are too short. "It's like when you shear a sheep and you get wool," James Tour, a nanoengineering and materials scientist at Rice University in Houston, told Science. "Those little wool fibres that first come off its back -- you can't make a blanket out of that. You have to somehow get it spun into long fibres that you can then put into a machine to get a wool sweater or blanket."

However Licht maintains that the process could be improved and extended. "It scales up very easily -- the entire process is quite low energy," the BBC quoted him as saying. He added the method could even be a "a reasonable path to bring down CO2 levels in the atmosphere" because it is solar powered, and results in a net lowering of carbon.

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How ambitious is that idea? Licht's team says that with an area "less" than 10 percent of the size of the Sahara desert, they could return global atmospheric carbon to levels seen before the development of mass industry -- even if we continue to emit carbon. Of course that will also leave us with a few potential problems' first, we have to find a lot of lithium, and second we'll have a lot of carbon nanofibres that we'll have to find uses for.

Not everyone is convinced. Ken Caldeira of the Carnegie Institution for Science in Stanford told New Scientist he was "extremely sceptical" and would be "highly surprised if these people have cracked this nut".

Dr Katy Armstrong, a chemical engineer at the University of Sheffield, told the BBC the idea was "promising and very interesting" but that "the process will need to deal with huge volumes of gas to collect the required amount of carbon, which could increase process costs when scaled up".